Nowadays, there are several devices for taking samples of soft tissue, these devices being generally used to extract, in a minimally invasive way, a sample of an organ from a human or an animal for analysis purpose. This extraction operation is generally known as biopsy and the used device is known as a biopsy gun.
Such a sampling device comprises in particular a sampling needle formed by a cannula and a stylet, an arming mechanism placed on a body and a trigger also placed on the body of the device.
The arming mechanism is used to partially retract the needle towards the inside of the body of the device, the device is placed near the organ from which one wishes to take a sample, then the trigger is pressed so that the needle can penetrate into the organ. The needle being formed by a stylet and by a cannula, the stylet penetrates into the organ, the cannula then covers the stylet. This stylet comprises at least one notch receiving the tissue to be taken. When the cannula covers the stylet, the tissue sample is trapped in the notch and is cut. The unit is withdrawn so that the sample(s) arranged between the stylet and the cannula can be taken. An example of application of such a device is taking tissues of the prostate.
The arming of the needle is generally achieved in two phases, namely the arming of the cannula in a first phase and the arming of the stylet in a second phase.
During sampling of tissues, it is frequent that the person who carries out the sampling has only one free hand, the other hand being used to hold other medical devices such as for instance an echographic probe. In this case, it is important to be able to manipulate the sampling device with one single hand. The manipulation implies here the arming of the cannula, the arming of the stylet and the release of the shot allowing for the sample to be taken.
Among the existing devices, which enable a manipulation with one single hand, one of them is described in the U.S. Pat. No. 7,153,275. This device is perfectly functional if it is manipulated in a correct way i.e. in most cases. However, it happens that certain bad manipulations cause problems. In particular when the arming of the cannula or of the stylet has not been achieved correctly, the shot can be released in an unintentional way. This can cause problems because a shot can be released in particular before the device is correctly placed near the organ of which one wishes to take a sample.
Another problem that has been encountered with this kind of device is due to the fact that in case of incorrect manipulation the arming mechanism and the shooting mechanism may become totally jammed, thus rendering the device unusable.
An additional problem can occur when a traction force is applied to the cannula or to the stylet. This can occur particularly while the biopsy gun is put in place to take a sample. In that case, the elements that enable to maintain the stylet and/or the cannula in the armed position can be released from their support and cause an unintentional shot.
This invention proposes to realize a tissue sampling device which has the advantages of the devices of the prior art i.e. it is possible to use this device with one hand. However, this device does not have the drawbacks of the systems of the prior art. Thus, even in case of bad manipulation, the shot is not released in an unintentional way. Moreover, the device cannot be jammed as a result of a bad manipulation.
Another advantage of the device of the invention relates to the fact that even in case of a relatively large stress applied to the needle, for instance while this needle is put in place to be used to take a sample, an unintentional shot cannot be triggered. This feature is obtained without increasing the strength necessary for arming the gun.
Furthermore, and especially in implementations of the invention wherein the sampling device may be a single-use sampling device, particularly the risk of jamming of the needle and/or the cannula individually or in relation to each other is reduced or eliminated. This is at least partly because the sampling device, and particularly the movable parts thereof e.g. the needle and the cannula, is then assembled correctly during manufacture leaving no risks of a user putting the parts together in the wrong manner as could very well be the case with re-useable sampling devices. In addition, a single-use device is also significantly less prone to risks of contamination, e.g. by bacteria on a user's hands.
Moreover, as a single-use sampling device may enable production tolerances different from those of a re-useable sampling device, it is in most cases less costly to manufacture than such re-useable sampling devices. Thereby, the improved security mechanisms against unintentional firing of the sampling device according to the different implementations of the invention may be particularly, but not exclusively, suitable for single-use sampling devices in order to meet any potential risks due to such different production tolerances as mentioned above.